[VadeRetro]

Most of the planets are so close to circles that on a piece of paper they would look just that. Again, the only two that would be even readily noticeable would be Mercury and Pluto.

For all that, there's some reason that their orbits are still wildly elliptical. I don't yet know what it is, but I expect it will be posted later by someone else.

[RadioAstronomer]

For all that, there's some reason that their orbits are still wildly elliptical

I think its because most solar system maps show then that way due to the artistic view of showing them on edgewise. :-)